了解宇宙是如何运行的（2010）

How the Universe Works S06E06

Part 3 Dec. 22, 2021, 7:23 p.m.

punched through the plane of the Milky Way.
随着快速移♥动♥的矮星系向银河系疾驰而去
As the fast-moving dwarf galaxy hurtles towards the Milky Way,
数百万颗恒星似乎正朝着碰撞的方向前进
millions of stars seem set on a collision course.
灾难似乎日不可避免
Catastrophe looks inevitable.
但表面现象可能具有欺骗性
But appearances can be deceptive.
当星系碰撞时，你可能首先想到的是
When galaxies collide, the first thing you might imagine
恒星碰撞，但实际上，这不会发生的
is that the stars collide, but actually, that doesn't happen.
星系大多是空旷的空间
Galaxies are mostly empty space.
如果你拿太阳来说，它真的很大…
If you took the Sun, which is really big...
它有一百万英里宽（约160万公里）……
It's a million miles across...
如果把它缩小到花粉的大小
And shrunk it down to the size of a piece of pollen,
那么星系本身的大小将是太平洋的两倍
the galaxy itself would be twice the size of the pacific ocean,
离太阳最近的恒星将在一英里（约1.6公里）之外
and the nearest star to the Sun would be a mile away.
这些小花粉粒永远不会相互碰撞
Those tiny pieces of pollen are never going to hit each other.
恒星间的距离是非常惊人的
The distances involved are staggering.
而在撞击的那一刻
And at the moment of impact,
两个星系的绝大部分恒星
most of the stars from the two galaxies
是完全碰不到对方的
miss each other entirely.
但这并不意味着银河系是安全的
But that doesn't mean the Milky Way is safe.
尽管恒星之间只是擦肩而过
Even though the stars just pass each other,
但当它们靠近时，它们确实会产生引力作用
they do gravitationally interact as they come close,
这种引力作用使它们
and this gravitational interaction sets them
走上了一条不同于它们
on a course that is different
原来运行的轨道
than if they were to live by themselves.
就像把一块石头扔进
In much the same way that taking a stone
平静的池塘然后在水中
and dropping it into a still pond
产生涟漪一样
creates ripples in the water,
这样一个星系撞击银河系
a galaxy like this slamming into the Milky Way
也会在整个圆盘上产生涟漪效应
can create ripple effects throughout the disk.
银河系的波纹
The ripples in the Milky Way
绵延数万光年
stretch across tens of thousands of light-years.
不过，这起肇事逃逸事件还不足以杀死银河系
Still, this hit-and-run isn't enough to kill the Milky Way.
它只会造成皮肉伤
It only causes a flesh wound.
但如果这个矮星系不是单独行动呢？
But what if this dwarf galaxy isn't acting alone?
如果它有同伙呢？
What if it has accomplices?
外面有很多矮星系
There are a lot of dwarf galaxies out there,
事实证明这些矮星系与像银河系
and it turns out collisions between these dwarf galaxies
这样的大星系之间的碰撞是很常见的
and big galaxies, like the Milky Way, are common.
这种事经常发生
They happen all the time.
现在，有几个矮星系
Right now, there are several dwarf galaxies
正在被银河系吞噬
that the Milky Way is swallowing up.
事实上，有一件非常有趣的事情
In fact, a really fun thing is that we're actually closer
我们实际上离其中一个星系的核心更近了……
to the core of one of these galaxies...
大犬座矮星系……
The Canis Majoris dwarf galaxy...
比我们到银河系核心的距离还要远
Than we are to the core of the Milky Way.
所以你在夜空中看到的一些星星
So some of the stars that you see around you in the night sky
实际上是来自不同星系的星星
are actually stars from a different galaxy.
那么，当所有这些矮星系聚集在一起
So, what happens when all these dwarf galaxies come together
并开始拉拽一个更大的星系时会发生什么呢？
and start pulling and tugging on a larger galaxy?
宇宙学家认为，银河系周围可能有
Cosmologists believe there could be hundreds of dwarf galaxies
数百个矮星系
surrounding the Milky Way.
与其中一个矮星系的碰撞
A collision with just one of these dwarf galaxies
可能会使银河系的旋臂产生涟漪
may have rippled the Milky Way's spiral arms,
但一群矮星系的碰撞
but a gang of dwarf galaxies
可能会产生更大、更致命的影响
could have a far bigger and far more deadly effect.
矮星系以及它们与像银河系这样的大星系
Dwarf galaxies and the way they interact with big galaxies,
相互作用的方式
like the Milky Way,
可以使我们的宇宙发生巨大的变化
can inflect tremendous change in our universe.
当它们撞击星系时，它们可以改变星系的结构
When they slam into a galaxy, they can change its structure.
如果没有这些矮星系
The Milky Way would not look anything like it looks today
银河系就不会是今天的样子
without those dwarf galaxies.
矮星系之间反复的碰撞
Repeated dwarf-galaxy collisions
可能从根本上改变了银河系本身的形状
could have radically altered the shape of the Milky Way itself.
它们的引力破坏可能在我们的星系中♥央♥
Their gravitational disruptions could have created a distinctive
创造了一个独特的、甚至是致命的特征……
and possibly fatal feature in the middle of our galaxy...
星系酒吧
The galactic bar.
银河系的中心被拉长了
The center of the Milky Way is elongated.
它的形状不像一个球体
Instead of it being shaped like a sphere,
更像一根棒子，棒子是由恒星以一种细长的
it's more shaped like a bar, and the bar is made by stars
绕轨道运行方式而形成的
actually orbiting in this sort of elongated way.
这条棒可能对星系的健康有害
And this bar can be bad for the health of the galaxy
因为它们的作用是让气体以漏斗的方式
because what they do is help to funnel gas
进入星系的核心
into the core of the galaxy.
这种气体的流失可能是阻止恒星形成的一种方式
The loss of this gas could be a way of stopping star formation.
银河系中心的棒状凸起
The bar-shaped bulge at the center of the Milky Way
会将我们星系的造星气体
sweeps our galaxy's star-building gas
扫进星系内核
into the galactic nucleus.
在这里，它被我们星系的
Here, it gets gobbled up
超大质量黑洞所吞噬
by our galaxy's supermassive black hole.
没有造星材料，就不会有新的恒星形成
Without the star-building material, no new stars can form,
星系就会消亡
and the galaxy dies.
那么，结案了吗？
So, is it case closed?
矮星系正在杀死银河系吗？
Are dwarf galaxies killing the Milky Way?
凶器是银河酒吧吗？
Is the murder weapon a galactic bar?
所以，有可能就是这些棒的形成
So, it's possible that the formation of these bars
帮助关闭了星系核心的恒星形成
helps turn off star formation in the very core of the galaxy,
但那只是星系的中心区域
but that's just the central regions of the galaxy.
这并不能解释旋臂中
That doesn't explain what's going farther out
更远的部分
in the spiral arms.
所以，如果银河系中恒星的形成真的停止了
So, if star formation really is shutting down in the Milky Way,
那也不是这根“棒”的错
it's not really the fault of the bar.
矮星系通过制♥造♥星系棒对银河系
Dwarf galaxies cause the Milky Way grievous bodily harm
造成严重的身体伤害
by creating the galactic bar.
但他们已经洗清了企图谋杀银河系的罪名
But they're off the hook for attempted galactic murder.
调查仍在继续
The investigation continues,
可能会出现戏剧性的转折
and it could be about to take a dramatic twist.
可能不是星系被谋杀了
It might not be that the galaxy's being murdered.
它可能会把自己吃死
It could just be eating itself to death.
银河系正在被消灭
The Milky Way is being killed off.
行凶者仍然逍遥法外
And the perpetrator remains at large.
调查此案的科学家们
Scientists investigating the crime
已经没有嫌疑人了
are running out of suspects.
但是寻找线索的工作仍在继续
But the hunt for clues continues,
所以天文学家们正在对这颗垂死的银河系星体进行体♥检♥
so astronomers are examining the dying body of the Milky Way.
我们的星系是一个由恒星组成的模糊盘
Our galaxy is a hazy disk of stars
周围环绕着炽热气体的光晕
surrounded by a halo of superheated gas.
它的直径超过10万光年
It's over 100,000 light-years across.
但它并不总是这么大
But it hasn't always been so big.
当你想到像星系这样
When you think about things so vast,
巨大而古老的物体时
so gigantic and ancient as galaxies,
你倾向于认为它们是
you're kind of tempted to think
非常稳定的物体
that they're very stable objects,
他们不会随着时间的推移而改变
that they don't change much over time,
但我们现在知道，我们自己的星系
but we now know that our own galaxy
是许多较小星系聚集在一起的“产品”
is the product of many smaller galaxies
随着时间的推移
that came together over time,
我们还会和其他星系一起碰撞
and there are other galaxies still colliding with us.
我们经常看到星系在互相吞噬
We see galaxies eating each other all the time.
它们会相撞，如果一个星系很大
They collide, and if one galaxy is very big
另一个星系很小
and one galaxy is very small,
那么小星系就会落入大星系，并被撕裂
the little galaxy falls into the big one, gets torn apart,
最后成为大星系的一部分
and becomes a part of that bigger galaxy.
银河系可能正在消亡
The Milky Way might be dying,
但它仍然是一个在宇宙中觅食的怪物
but it's still a monster foraging through the universe,
在整个吞噬较小的星系
swallowing smaller galaxies whole.
当然它也吞噬了他们的星星
It consumes their stars.
但它也同样品尝了造星气体的味道
But it also has a taste for their star-building gas.
而且它不需要与其他星系发生碰撞
And it doesn't have to collide with other galaxies
就能以它们为食
to feed off of them.
一个星系的命脉是氢气
Now, the lifeblood of a galaxy is hydrogen gas.
这才是真正创造新恒星的原因